1. Field of the Invention
The present invention generally relates to a tool for machining small component parts and, more particularly, to a compact, multi-axis, multi-tasking small part machine tool.
2. Background Description
Practically every major industry today has the need for miniature component parts. For example, in the electronics and computer industries, smaller means faster information transfer, which results in higher input, output, and processing rates, and is particularly important in structures for mounting and interconnecting chips and for heat transfer. In the medical industry, smaller biomedical devices mean less invasive surgical procedures, thus resulting in quicker patient recovery times. In the aerospace industry, smaller aerospace components mean lighter weight and less space, thus resulting in larger potential payloads and/or improved performance. In the automotive industry, smaller automotive components reduce weight, thus increasing fuel efficiencies. As for consumer products, smaller means greater portability and convenience. Regardless of the industry, the demand for making things smaller is growing rapidly and manufacturers face continual challenges in making small components.
Milling machines, both CNC (Computer Numerical Control) and manually operated, remove material from flat surfaces, recesses and apertures of a stationary workpiece utilizing a rotating, multipoint, traveling cutting tool. Parts often require more than just one cutting tool to complete, so several cutting tools may be placed into and taken out of the milling spindle manually or by use of an automatic tool changer. Another option, if more than one cutting tool is required, is to “gang” two or more milling spindles onto a longer traveling slide to enable using each tool without necessitating removal of any given tool from its spindle. Milling machines with CNC controls and automatic tool changers are commonly referred to as machining centers. Milling machines and machining centers normally have three linear axes of motion, but can also have one or more rotary axes of motion as well. However, milling machines are not well-suited to forming radially symmetrical surfaces with high precision.
Lathes generally remove material from a rotating workpiece utilizing a traveling, single point cutting tool and can do so with much improved precision compared with milling machines for non-planar surfaces. When more than one cutting tool is required, the cutting tools can be changed manually, automatically or “gang tooled” onto a slide whereby each tool can be utilized by simply changing the axis position. Lathes with CNC controls and tool turrets are commonly referred to as turning centers. Lathes generally have two linear axes of motion, but can have rotary axes (generally used to control spindle positioning) and additional linear axes as well (e.g., a third axis can be added to the main tool slide for what is commonly called a “Y-axis” turning center or an additional tool slide with two more axes of movement can be added to make a “four-axis” turning center). Because many lathes used to machine small parts are primarily intended for hobby shop or home shop machining, they are not well suited for industrial applications.
Traditionally, lathes are used to machine round parts and milling machines are used to machine prismatic parts or part features. Turned parts with milled features are typically machined in a lathe and are then transferred to a milling machine to have those operations performed. However, for smaller components, handling, re-orienting, and re-fixturing and/or chucking the part for a second or third machining operation becomes extremely difficult and a source of potential error or inaccuracy. It is much easier and more expeditious to complete the part, including all turning and milling operations, in one set-up and machining operation which also removes a source of error. The ability to perform turning and milling operations in one machine, is commonly referred to as multi-tasking.
Although industrial machines do exist that perform both types of operations, such as CNC controlled Swiss-type machines for small parts, these machines often require multiple duplicate axes to perform these additional operations. Each axis is primarily comprised of the following parts: the machined slide casting, a set of linear guide ways and trucks, a ball screw and nut, ball screw support bearings, servo motor, servo drive, coupling, a set of pulleys, a timing belt, electrical wiring, and fasteners. This requirement tends to sacrifice simplicity for higher production rates and/or the ability to multi-task. However, market demand for product customization often supplants the need for higher production rates and thus increases the importance of simplicity, flexibility, and reduced set-up times. Furthermore, in large part due to their numerous axes, Swiss-type machines are quite expensive.
Further, manufacturers may also be restricted by the type of raw material they may use when machining small parts. For example, since the operation of Swiss-type screw machine depends on the utilization of bar stock as the raw material, this precludes manufacturers who are utilizing these machines from manufacturing small parts formed by castings, forgings, sawed bar stock slugs, or newer, near net shape raw material alternatives (e.g. metal injection moldings).
Small part machining also has a need for a machine tool design that is very compact. There are many benefits for a compact small part machine tool including, but not limited to, simplicity, rigidity, economics of design, less use of floor space, and more efficient machine movements. Although these are important criteria for all machine tool designs, compactness is especially critical when designing a machine tool for small part machining. At this reduced scale, cutting tools and tool holders tend to interfere with work holding devices, other cutting tools or tool holders, or parts of the machine tool itself. In order to avoid such interference, the tools or workpiece are frequently extended from their collets or holding devices and left unsupported. This leads to the possibility of tool and workpiece flexing, vibration, breaking, etc. A more compactly designed machine tool reduces both interferences and the undesirable necessity of tool and/or workpiece extension while providing better tool rigidity or reduced flexure.